A data center may be defined as a location, for instance, a room, that houses computer systems arranged in a number of racks. A standard rack or an electronics cabinet is defined as an Electronics Industry Association (EIA) enclosure, 78 in. (2 meters) high, 24 in. (0.61 meter) wide and 30 in. (0.76 meter) deep. These racks are configured to house a number of computer systems, about forty (40) to 200 or more systems. The computer systems typically include a number of printed circuit boards (PCBs), mass storage devices, power supplies, processors, micro-controllers, and semi-conductor devices that dissipate relatively significant amounts of heat during their operation.
One or more air conditioning (AC) units are typically employed to supply cooling airflow to dissipate the heat generated by the computer systems. It is beneficial to control the moisture content in the airflow supplied by the AC units because too much moisture increases the risk of condensation forming on the computer systems and too little moisture increases the risk of electrostatic discharge issues. In order to substantially maintain the moisture content within a desired range, the AC units are often equipped with a humidifier/dehumidifier configured to add or remove moisture content in the cooling airflow. AC units equipped with these devices are also typically equipped with humidity sensors positioned at the returns to detect the relative humidity of the airflow returning into the AC units through returns. In addition, the AC units control the moisture content of the cooling airflow to meet a predetermined relative humidity set point at the returns.
If designed and arranged appropriately, and if the desired relative humidity range is broad, such as, between 20%-80%, the AC units are typically capable of maintaining the relative humidity levels within the desired range. However, because the humidity control is based only on the relative humidity detected at the returns of the AC units and because relative humidity is a function of temperature, when there is a problem, such as, if one of the AC units supplies overly cool airflow, certain areas of the data center may receive the cooler air, which may lead to the formation of condensation in those areas. In addition, the AC units may operate in relatively energy inefficient manners because one AC unit may be humidifying while another AC unit is dehumidifying in supplying cool airflow to the same areas in the data center.
It would thus be desirable to have humidity control in a structure, such as, a data center, without suffering from the drawbacks and disadvantages associated with conventional humidity control arrangements.